Hi Embee,
You are welcome and thank you for your kind words about our site. You’ve certainly done a quite bit of research and will be moving probably much faster through your next decisions.
In general, most foam mattresses (including latex) don’t have or even really need side support if they have a support core that is firm enough and the comfort layers aren’t too thick and/or soft. You are correct that sometimes because of latex’s point elasticity… those who sit on the very outside edge of the mattress (instead of sitting with the bodyweight more into the middle of the mattress) or who sleep with more concentrated weight on the outside few inches of their mattress may find themselves sinking down more than they like even though this isn’t normally an issue when sleeping on the mattress. There are some solutions for those who prefer a firmer edge then there are a few latex mattresses that use what’s called a “racetrack” perimeter where the outer few inches of the latex support core is surrounded with a firmer foam. Unfortunately, most of the time this firmer foam is a much less durable (but firmer) polyfoam which will soften and break down sooner than the latex and what starts out as a positive can become a negative over time (depending on the density of the polyfoam this can sometimes be a fairly short time). A better solution would be to find a mattress with a firmer latex in those cases where perimeter support is preferred rather than less durable polyfoam but this is an uncommon construction for latex, but most of the time.
While your husband’s BMI is not so far apart from yours, with his chronic backache and back sleeping positions he’d certainly do best with a firmer sleeping surface. For your side sleeping primary position however you’d generally need a bit more pressure point relief on the surface to accommodate the wider dimensional variances between the shoulders and the hips and the waist, which you seem to have traded for better edge support.
In response to your first alternative, I certainly understand your apprehension of "process repeat " especially when you were so close to something you both liked … albeit in different configurations. 3 zippered layers would certainly give you more options to fine-tune the feel. Assuming that you find something that best suits your own sleeping needs I’d keep in mind that it may be at the expense of being suitable for your husband and that you may need to be giving up on the edge support while sitting. Having mattress in a dual split configuration could prove useful in your situation and you may wish to consider it.
Even though there is no formula that can predict with any certainty what type of layering you may do best with that can possibly be more accurate than your own personal experience, you can use insights you’ve gained in your online purchase along with guidance of a knowledgeable and experienced retailer/manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness, etc.) and the options they have available that may be the best “match” for you based on the information you provide them. They will know more about “matching” their specific mattress designs, options, and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else. If you chose to stick with the local store alternative(s), you’d still need to consider the comfort/support suitability for your husband.
Assuming that and that the base is strong enough and supported on the floor well enough to hold the weight of the latex mattress and the people that sleep on it and assuming that the slats have no flex that there is a less than 3" gap between them, placing a solid surface on slats would not have impact on the feel and firmness of the mattress If anything it would have an effect on the breathability and ventilation of the mattress as a whole.
As far as the pillowtop goes… pillowtop is just a tailoring process and not an indicator of the softness, quality or specific materials contained within a mattress and you would not have the ability to fine-tune this mattress should you need it.
I hope this gives you a bit of direction in moving forward with your next decision
Phoenix
